Use wxDELETE() and wxDELETEA() when possible.

Use wxDELETE[A]() functions which automatically NULL out their arguments after
deleting them instead of doing it manually.

Closes #9685.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64656 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/window_osx.cpp

@@ -257,11 +257,7 @@ wxWindowMac::~wxWindowMac()
 
     // delete our drop target if we've got one
 #if wxUSE_DRAG_AND_DROP
-    if ( m_dropTarget != NULL )
-    {
-        delete m_dropTarget;
-        m_dropTarget = NULL;
-    }
+    wxDELETE(m_dropTarget);
 #endif
 
     delete m_peer ;